Of this list I voted Vader, but there are a few others very worthy of mention. Maleficent being among the best of them as Darkstone suggests. Saruman rolls off the tongue nicely and his lesser-used name of Curunir just evokes a "cunning mind". Can't go wrong with the ancient Greek classic of Medusa. Gothmog evokes the great Japanese creatures, speaking of which, Godzilla and Mothra deserve mention. Even though I'm not a Potter fan, Severus Snape IS a good name. Voldemort just doesn't evoke anything special though.